1. Field of the Invention
The present invention generally relates to optical plates, and more particularly to a prism sheet for use in, for example, a liquid crystal display (LCD).
2. Discussion of the Related Art
FIG. 4 is an exploded, side cross-sectional view of a typical liquid crystal display device 100 employing a typical prism sheet 10. The liquid crystal display device 100 includes a housing 11 and a plurality of lamps 12 disposed in the housing 11. The liquid crystal display device 100 further includes a light diffusion plate 13, a prism sheet 10, an upper light diffusion film 14 and an LCD panel 15 stacked on the housing 11 in that order. The lamps 12 emit light, and an inner wall of the housing 11 is configured for reflecting some of the light upwards. The light diffusion plate 13 includes a plurality of embedded dispersion particles. The dispersion particles are configured for scattering received light, and thereby enhancing the uniformity of light that exits the light diffusion plate 13.
Referring to FIG. 5, the prism sheet 10 includes a plurality of V-shaped structures 102 on a top surface 101. The V-shaped structure 102 extends along a straight line from one end to the other end of the prism sheet 10. A plurality of V-shaped structures 102 are regularly and periodically arranged parallel to each other. The V-shaped structures 102 are configured for collimating received light to a certain extent.
In use, light emitted from the lamps 12 enters the prism sheet 10 after being scattered in the diffusion plate 13. The light is refracted by the V-shaped structures 102 of the prism sheet 10 and is thereby concentrated, so that a brightness of light illumination is increased. Finally, the light propagates into an LCD panel 15 disposed above the prism sheet 10. However, it is prone to occur moire pattern interference on the LCD panel 15 due to the V-shaped structures 102 are aligned similarly to the LCD pixels. In order to decrease the moire pattern interference, the liquid crystal display device 100 needs to add an upper light diffusion film 14 between the prism sheet 10 and the LCD panel 15. Although the upper light diffusion film 14 is disposed on the prism sheet 10, a plurality of air pockets still exists at the boundary therebetween. When the liquid crystal display device 100 is in use, light passes through the air pockets, and some of the light undergoes total reflection at one or another of the corresponding boundary. In addition, a amount of light are absorbed by the upper light diffusion film 14. As a result, a light brightness of the liquid crystal display device 100 is reduced.
Therefore, a new prism sheet is desired in order to overcome the above-described shortcomings.